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M. SMODI[ et al.: THE CONTENT OF RARE-EARTH ELEMENTS IN MOBILE-PHONE COMPONENTS259–268

THE CONTENT OF RARE-EARTH ELEMENTS INMOBILE-PHONE COMPONENTS

VSEBNOST ELEMENTOV REDKIH ZEMELJ V KOMPONENTAHPRENOSNIH TELEFONOV

Martin Smodi{1, Niko Samec1, Borut Kosec2, ^rtomir Donik3, Matja` Godec3, Rebeka Rudolf1

1University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia2University of Ljubljana, Faculty of Natural Sciences and Engineering, A{ker~eva cesta 12, 1000 Ljubljana, Slovenia

3Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana, [email protected]

Prejem rokopisa – received: 2017-05-28; sprejem za objavo – accepted for publication: 2017-11-23

doi:10.17222/mit.2017.064

In the present article, we present a study in which we want to establish whether it is possible to determine the presence and massfraction of rare-earth elements (REEs) in the components of discarded mobile phones. In order to do so, we have selected thefollowing characterization techniques and microchemical analysis methods: Energy Dispersive Spectroscopy (EDS) and Wave-length Dispersive Spectroscopy (WDS). To confirm the hypothesis, we have randomly selected six models of mobile phonesfrom different manufacturers, produced in the period 2004-2015. As representative samples of mobile phone components, weanalysed the magnets (containing REEs (vibrator and speaker). To confirm the presence and determine the content of REEs inindividual components of mobile phones, we used Light Microscopy (LM) and Scanning Electron Microscopy (SEM) in combi-nation with microchemical analyses: Energy Dispersive Spectroscopy (EDS) and Wavelength Dispersive Spectroscopy (WDS).Our research has shown that the magnets consist of a magnetic core (which is composed of Fe-Nd-Pr and in newer mobilephones is also enriched with Gd) and of a corrosion resistant coating with a thickness of 24–26 μm. The latter is composed ofthree layers (Ni-Cu-Ni). With extensive microchemical analyses EDS and WDS on the surface of magnetic cores, we haveestablished that the average content of REEs (Nd, Pr, Gd) in both magnets (vibrator and speaker) of a mobile phone is roughly13.5 % of mass fractions or 0.082 g.

Keywords: mobile phones, components, rare-earth elements (REE), chemical structure, characterization, electron and opticalmicroscopy, microchemical analysis

V prispevku prikazujemo raziskavo, s katero smo `eleli ugotoviti, ali je na podlagi ustrezno izbranih tehnik karakterizacije inmikrokemi~nih analiz mo`no dolo~iti prisotnost in masni dele` elementov redkih zemelj (ERZ) v sestavnih komponentah odslu-`enih prenosnih telefonov. Za potrditev hipoteze smo naklju~no izbrali {est modelov prenosnih telefonov razli~nih proizva-jalcev, izdelanih v obdobju 2004–2015. Kot reprezentativne vzorce sestavnih komponent prenosnih telefonov smo analiziralimagnete (vibrator in zvo~nik), ki vsebujejo ERZ. Za potrditev prisotnosti in dolo~itev vsebnosti ERZ v posameznih sestavnihkomponentah prenosnih telefonov smo uporabili svetlobno (SM) in vrsti~no elektronsko mikroskopijo (SEM) v kombinaciji zmikrokemi~nima analizama: energijsko disperzijsko spektroskopijo (EDS) in valovno disperzijsko spektroskopijo (WDS). Na{epreiskave so pokazale, da so magneti sestavljeni iz magnetnega jedra, ki je sestavljeno iz Fe-Nd-Pr (NdFeB), v novej{ih pre-nosnih telefonih pa je obogateno tudi z Gd ter iz protikorozijske za{~itne prevleke z debelino 24–26 μm, ki je sestavljena iz trehplasti (Ni-Cu-Ni). Z ob{irnimi mikrokemi~nimi analizami EDS in WDS na povr{ini magnetnih jeder je bilo ugotovljeno, da jepovpre~na vsebnost elementov redkih zemelj (Nd, Pr, Gd) pribli`no 13,5 mas. % oziroma 0,082 g skupno v obeh magnetih(vibratorja in zvo~nika) mobilnega telefona.

Klju~ne besede: prenosni telefoni, komponente, elementi redkih zemelj (ERZ), kemijska sestava, karakterizacija, elektronska inopti~na mikroskopija, mikrokemi~na analiza

1 INTRODUCTION

Rare-earth elements (REEs) are becoming very use-ful materials, for they represent one of the most import-ant components in advanced technologies, without whichwe cannot imagine the production of high-tech devicesand further development of green technology/greenenergy programmes. The usefulness of REEs is related totheir unique chemical/physical, catalytic, electrical, mag-netic and optical properties.1–3

Their end uses can be can be grouped into two broadcategories. In the first category, rare earths act as špro-cess enablers’, i.e., they are used in the production pro-cess but they are not actually contained in the end pro-duct. For instance, light rare earths are used in polishing

powders (15 %) in the glass, electronics, and opticsindustries; they also serve as fluid-cracking catalysts(13 %) in refining and other chemical processes. In thesecond category, REEs act as šproduct enablers’ that giveadvanced materials unique properties that play a key rolein the performance of high-tech products. REE-basedpermanent magnets are currently perhaps the mostimportant of these product-enabling applications, as theaddition of rare earths can boost the force of permanentmagnets (20 %), which is usefully applied in productssuch as electric motors and turbines. Another key appli-cation pertains to REE phosphors (7 %) used in lightingand displays, enabling technologies such as compactfluorescent lamps and LCD screens. Other importantuses are in batteries (8 %); in the coating of autocatalysts

Materiali in tehnologije / Materials and technology 52 (2018) 3, 259–268 259

UDK 546.65:621.395.721.5:67.014 ISSN 1580-2949Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 52(3)259(2018)

(6 %); and as additives in high-tech alloys (10 %), glass(7 %), and ceramics (5 %), etc.4–9 Great usability ofREEs in advanced technologies, consequently, generatesan extreme demand, which is the main issue in thedomain of REE supply. The fact is that the EuropeanUnion (EU) does not have enough REEs, thereforeapproximately 90 % has to be imported, primarily fromChina.10 China has been a leading force in the REEmarket for the past 20 years and today it operates theglobal market with an 82.7 % share. It is estimated4,5,9

that the demand for REEs will increase by 20 % by 2018and by 2020 by over 50 %. The global REE market hasalready crashed in the past, which led to the implemen-tation of Chinese quotas in 2010/11. This led Europeangeological surveys to intensify their data-collationefforts, and spurred companies, from both Europe andabroad, to do more independent exploration projects.However, most of them were not implemented in miningpractice due to questionable economic viability of suchprocedures.9 Moreover, efforts in scientific research wereintensified, namely in the domain of recycling proce-dures pertaining to REE recycling of waste productssuch as scrap electronics, predominantly carried out on alaboratory research level.11 The quantity of wasteelectrical and electronic equipment in the EU in relationto the rest of the world is increasing rapidly (by 3 % to5 % on an annual basis).12 Thus, the EU Directive onWaste Electrical and Electronic Equipment (WEEE)13

was adopted in July 2003 and revised in 2012. It aimstowards re-use, recycling and other forms of recovery ofwaste electrical and electronic equipment,14 whichreduces the disposal of waste and contributes to theefficient use of resources and the retrieval of valuablesecondary raw material. With this Directive13 minimumgoals that apply to the processing and recycling of wasteelectrical and electronic equipment from the categoriesof Information Technology and Telecommunicationswere set. This also includes mobile phones, which arethe subject of the present study.

According to the data,15 in Europe 160 million cellphones per year are discarded, sent to landfills andremain uncollected and unrecycled, which represents anannual material loss in the amount of 500 million USdollars. According to the analyses of the global marketfor mobile phones,16 1917 million mobile phones werereleased on the world market, 210.3 million of whichwere on the European one. Analysts estimated16 that in2016, the amount of the global market of released mobilephones soared on average by 7 %, and consequently, in2018, over two billion will be released on the worldmarket. The amount of WEEE will grow correspond-ingly, causing significant adverse effects on theenvironment. A possible solution to this problem mightbe the recycling of discarded mobile phones along withthe recovery of valuable secondary raw material andREEs from their constituent components. Recycling amillion cell phones results in obtaining 9.000 kg Cu, Ag

250 kg, 24 kg and 9 kg of Au and Pd, and a certainamount of REEs.11 We should not ignore the fact thatgetting metals with modern recycling processes is 2 to 10times more energy efficient than smelting metals frommineral ores. Recycling also generates a smaller per-centage of CO2 emissions and has significant benefitscompared to mining in terms of land use and hazardousemissions. For REEs, the specific emissions avoided bystate-of-the-art recycling are reported as being evenhigher.9 REE recycling would also provide significantbenefits with respect to groundwater protection, acidifi-cation, eutrophication, and climate protection. Thisreport also states that the recycling of REEs will notinvolve radioactive impurities, as is the case withprimary production.5

Notwithstanding the economic viability of recyclingdiscarded mobile phones, we are bound by the EuropeanDirective on WEEE to implement rapid recycling andthereby reducing the disposal of WEEE, and increasingresource efficiency and the recovery of valuable secon-dary raw material from discarded mobile phones.

In sum, on the one hand there is an extreme demandfor REEs due to the highly versatile use in advancedtechnologies, with European high-tech industry beingcompletely dependent on their availability on the globalmarket. On the other hand, we have a year-on-yeargrowth in the production of high-tech electrical and elec-tronic devices with a consequent rise in the quantities ofWEEE and their uncontrolled deposition in the environ-ment, which has an increasingly negative impact on theenvironment. Due to the still insufficiently regulateddomain of regaining REEs and secondary raw materialfrom WEEE, there are major energy, raw material andfinancial losses, causing an unnecessary burden on theenvironment. The solution to this problem might be theaccelerated multi-element recycling of WEEE, includingREE in discarded mobile phones treated in the presentstudy. Based on the above, the main purpose of the studyis to determine the content of REEs in the constituentcomponents of discarded mobile phones.

2 EXPERIMENTAL PART

For the study, six different models of discarded mo-bile phones from different manufacturers, manufacturedin the period 2004–2015, were selected at random. Everymobile phone was stripped down to basic functionalcomponents: the electronic circuit, microphone, speaker,vibrator, camera, display, battery, etc. In the first phaseof the experimental work, we performed a process ofidentifying mobile phone components which could con-tain REE. By doing so, we wanted to determine whetherseveral different REE are present in the key componentsand what their contents are (in mass fractions, w/%).Based on a review of specialist literature ("state-of-the-art"), we decided to limit the selection to two represen-tative samples of the constituent components (a vibrator

M. SMODI[ et al.: THE CONTENT OF RARE-EARTH ELEMENTS IN MOBILE-PHONE COMPONENTS

260 Materiali in tehnologije / Materials and technology 52 (2018) 3, 259–268

and a speaker) of discarded mobile phones, for which weassumed, based on a literature review,9,17 that their con-stituent components are made of magnetic materials, inwhich, with the proper technique of characterization andanalytical techniques, we could identify the presence ofREEs and determine their content. The scheme of theidentification process carried-out is shown in Figure 1.

Before conducting the study, we selected relevantcomponents, recorded and tagged them, extracted mag-net samples, documented and tagged them appropriately(Figure 2) and weighed them on a digital laboratoryscales.18 An overview of representative samples ofmagnets for their characterization with LM and SEMmicroscopy and EDS and WDS analysis is presented inTable 1.

Table 1: Overview of representative samples of magnets for the cha-racterization of the LM and SEM microscopy

Tag of theselectedmobilephone

Year ofproduction

of amobilephone

Tag of representative samples ofmagnets

V - vibrator or Z - speaker

The weight of arepresentative sample

of the magnet (g)ZV - speaker/longitudinal

sectionZP - speaker/cross section

VV - vibrator/longitudinal

sectionVP - vibrator/cross section

Z(speaker)

V(vibrator)

V1 2015 V1-ZV V1-VV 0.354 0.148

V2 2008 V2-ZV

V2-ZPV2-VV 0.202 0.395

V3 2007 V3-ZVV3-VV

V3-VP0.416 0.259

V4 2004 V4-ZV V4-VV 0.603 0.231V5 2008 V5-ZV V5-VV 0.473 0.440V6 2006 V6-ZV V6-VV 0.069 0.071

For the purpose of LM microscopy, we used anoptical metallurgical microscope Nikon Epiphot 300 thatallowed magnification up to 1,000 times and imple-mented digital photography and image analysis usingOlympus AnalxSIS 3.2. software. Samples of LM micro-scopy were properly treated with a conventional metallo-graphic procedure. The surface of magnet samplesV2-Zp and V3-Vp was examined transversely, while thesurface of magnet samples V1-VV, V1-ZV, V2-VV,V3-VV, V3-ZV, V4-VV, V4-ZV, V5-VV, V5-ZV, V6-VV

and V6-ZV was examined longitudinaly.18 For thesamples of magnets that were taken transversely, thepurpose was to identify the thickness of individual layersof the corrosion-protective coating, while the purpose oflongitudinally examined magnet samples was to get theintegral impression of the microstructure of their cores.For each magnet sample, six LM images of the micro-structure of their surfaces at different magnificationswere captured and analysed. Those LM images served asthe basis for the quantitative metallographic analysis.The grain size and percentage of porosity in the micro-structure of the magnetic cores were determined with theASTM19 planar analysis method with the assumption thatthe crystal grains are square-shaped.

An in-depth examination of the microstructure wasperformed with the SEM microscope JEOL JSM 5610with the EDS IXRF SYSTEM, Inc. 500 Digital Pro-cessing analytical technique as well as with the SEMmicroscope Sirion 400 NC with the EDS Oxford INCA350 analytical technique. For examination purposes, themagnet samples were thoroughly polished. By doing so,



Figure 1: Schematic representation of the experimental work carried out

we removed the reaction products generated by the che-mical etching preparation. Thus, we ensured the surfacesof representative samples had an identical starting point.In the first part, we tested the chemical composition andthe presence of REEs on the exterior of the vibrator bymeans of WDS analysis. The analysis parameters were:an accelerating voltage of 20 kV, current of 60 nA andsignal accumulation time of 15 s. We chose the LiFcrystal for the analysis, as it is the most suitable one forthe applied wavelengths. For characterization with SEMmicroscopy, the following setup parameters wereapplied: an accelerating voltage of 20 kV, various magni-fications 35-, 1,500-, 1,700- and 2,500-times incorrelation to the EDS analysis, a working distance of20 mm from the sample and an average time of signalaccumulation of 100–120 s.

The magnet sample of the vibrator V2-VV was exa-mined without prior removal of the corrosion-protectivecoatings. On samples V2-ZP, V3-VP anticorrosioncoating on the transverse surface was examined, whilethe magnet samples V1-VV, V1-ZV, V2-VV, V3-VV,V3-ZV, V4-VV, V4-ZV, V5-VV, V5-ZV, V6-VV and V6-ZV

were examined on the longitudinal surface after re-moving the anti-corrosion protection layer.18

3 RESULTS AND DISCUSSION

The research work limitations were: the constantlychanging technology of mobile phone manufacturing, thelarge number of manufacturers, many different models ofmobile phones; for the research it was necessary todisassemble mobile phones down to their basic compo-nents, the examined representative samples (vibrator andspeaker) were magnetic and very small in dimensions.The magnetism of the samples interfered with thefocused beam of electrons in the scanning electronmicroscope, which reflected in the distortion andreduced resolution of the electronic image, whereas themagnetism had a negligible effect on the conduct of themicrochemical analysis. We conducted the study withthe presumption that we have ensured the appropriatesystematic method of collection of discarded mobilephones and that we included representative samples. Ourassumption for the quantitative microstructural analysis,based on the carried-out microchemical analyses, wasthat the microstructure of the samples’ magnetic cores issintered and homogeneous by volume in its chemicalcomposition, that the rudimentary crystal grains aresintered microstructures of the magnetic core andsquare-shaped, and that the porosity is in most casesvisible as dark areas, which are uncovered during themicrostructural examination of the etched surface of thesamples’ magnetic cores with an optical microscope.

The study was limited to the LM and SEM charac-terization techniques, which allow us insight into themicrostructure (size and shape of the crystal grains,porosity, thickness of individual layers of protective

coating) of the representative samples of the two maincomponents (the vibrator and speaker) of discardedmobile phones. In addition, we used semi-quantitativeEDS and WDS microchemical analyses. These analyticalmethods have enabled us to determine the presence andcontent of REE in selected samples of the constituentcomponents of discarded mobile phones and theirdistribution over the surface of the sample. Due to thecomplexity and the time-and-money-consuming natureof the WDS analysis, we conducted a test for the pre-sence of REEs only on one of the vibrator sample’sexterior (V2-V). Given that we primarily were lookingfor the presence of REEs, we conducted an analysiswithout applying the aforementioned standards.

3.1 Microstructural analysis

The anti-corrosion coating of the sample V3-VP’smagnet is shown in Figure 3a, where, in the upper partof the cross-sectional area, the anti-corrosion coatingwith the estimated thickness d) of 24.38 μm is clearlyvisible, and consists of three layers. The estimatedthickness of the upper layer a) is 9.03 μm, the centrallayer b) 7.81 μm and the lower layer c) 7.54 μm. Themicrostructure of the sample in the magnetic core of thevibrator (V3-VV) is shown in Figure 3b and is typical ofa sintered state; crystal grains are mainly polygonal inshape, irregular rounded crystal grains are also partlypresent. Our calculations have shown that the crystalgrains are on average 5.4 μm in size and that the porositypercentage is less than 1 %.

The loudspeaker’s magnetic core sample (V3-VZ)microstructure is shown in Figure 3c, from which it isapparent that it is typical for a sintered state; crystalgrains are mainly of polygonal shape, but also of irregu-



Figure 2: Display case of an exhibited disused mobile phone: a) Anelectronic circuit with a speaker and a vibrator, b) Exhibited speakerwith the sample of the magnet (VX-Z), c) Exhibited vibrator with thesample of the magnet (VX-V)

lar curved shape. Furthermore, calculations have shownthat crystal grains are, on average, 6.7 μm in size andthat the porosity percentage is less than 1 %.

Table 2: Characteristics of representative samples of the magnets: a)the thickness of each layer of the corrosion protective coating, b) thegrain size of the magnetic core(a)

Representativesample of

magnet

The thickness of the layer of corrosionprotective coatings (μm)

a b c d (a+b+c)V2-ZP 5.19 6.23 14.54 25.96V3-VP 9.03 7.81 7.54 24.38

(b)

Representative sample ofmagnet

Grain size(μm)

V1-VV 8.5V1-ZV 10.6V2-VV 7.2V2-ZV 5.6V3-VV 5.4V3-ZV 6.7V4-VV 9.6V4-ZV 9.3V5-VV 10.9V5-ZV 8.1V6-VV 9.0V6-ZV 6.0

Table 218 shows our calculation: the thickness of theindividual layers of the corrosion protective coatings andcrystal grain size in the magnetic core of the individualsamples. Comparison of microstructures and calculatedgrain sizes in samples from groups of both vibrators andspeakers with production years from 2004 to 2007(V4-VV, V4-ZV, V3-VV, V3-ZV) shows that the crystalgrains are similar in size and of comparable distribution.Based on this, we can conclude that the magnets of vib-rators and speakers are made with a very similartechnique of sintering. For the samples with the manu-facture dates of 2006, 2008 and 2015 (V6-VV, V6-ZV;V2-VV, V2-ZV; V5-VV, V5-ZV; V1-VV and V1-ZV), wefound that the crystal grains are different in size, as wellas in microstructure. We can conclude that different tech-niques of sintering–manufacturing are involved, depend-ing on the intended use of the magnet. In magnetsamples of vibrators V2-VV, V4-VV, V5-VV and V6-VV,

the crystal grains are larger than in magnet samples ofspeakers V2-ZV, V4-ZV, V5-ZV, V6-ZV. In magnetsamples of vibrators V1-VV and V3-VV the crystal grainsare smaller than in magnet samples of speakers V1-ZV

and V3-ZV.We expected to get a clear view of the typical

topographic details of the analysed magnet samples’surface directly from the SEM microscopy. We deducedfrom the analysis that the effect of the strong magneticfields of analysed magnet samples caused distortion,poor resolution, time lag and poor sharpness of surfaceimages. For this reason, the generated images of the

SEM microscopy were not as high-quality as they can beif generated with SEM microscopy of other non-magne-tic samples.

3.2 Microchemical analyses of EDS and WDS

WDS Analysis

In the WDS microchemical analysis of the housing ofthe vibrator V2-V, the signal at the "peak" site was weak-er than the "background" signal. In the analysis process,approximately 800–2000 cts were captured. Whentesting for the REEs, whose presence we predicted in thehousing of the vibrator, the results showed that the REEconcentration in the given sample was below the detec-tion limit (the latter was set at 3 sigma above the back-ground). To further confirm the presence of REEs, weperformed a spectral scan of the LiF crystal, which isbest suited for the REE in the Ce-Lu period of the perio-dic table. In this area, Cu, Ni and Fe, which constitutethe main elements of the sample vibrator’s housing(Figure 4), also peaked. The findings from the WDSmicrochemical analysis of the vibrator housing V2-Vconfirmed the presence of Cu, Ni and Fe, as evident fromthe spectrum and the position of the peaks of theseelements (Figure 4). In contrast, the position of thepeaks of REE is almost null and void. Based on this, weconcluded that the presence of REEs in the analysedhousing of the V2-V vibrator is below the detectionlimit, or the REEs were not present.18 Figure 4 shows the



Figure 3: LM microstructure of the surface of samples: a) anti-corrosion coating sample V3-VP, b) the magnetic core sample V3-VV,c) the magnetic core sample V3-ZV

mapping of the characteristic spectrum of the analysedvibrator housing sample V2-V in the WDS microchemi-cal analysis, taken at a the lowest speed (for the wholeLiF crystal, in this case approximately 4 h) with theselected place of analysis.

EDS analysis

The EDS microchemical analyses of the V2-Vvsample have shown that REEs are not present in thesample, as predicted; the EDS analysis only confirmedthe presence of Cu, Ni and Fe (Figure 5). On this basis,we concluded that the magnet sample V2-Vv has anti-corrosion protection, as do all the other reference sam-ples of magnets. Next, the layers of the anti-corrosioncoating were removed, thus enabling tests directly on thesurface of the magnetic cores. These samples were thenproperly metallographically prepared for further EDSanalysis.

In the first stage we performed an EDS analysis ofthe anti-corrosion coating layers on magnet samplesV2-ZP and V3-VP, and then analysed the distribution ofelements in each layer. An example of characteristicEDS spectrums of the anticorrosion coating layers withselected places of analysis and contents of detected

elements on the magnet is the typical sample V3-VP,shown in Figure 6. Microchemical EDS analysis ofanticorrosion coating layers of the V2-ZP sample hasshown the presence of Fe, Ni and Cu in layers, namely inthe following content:Place (1): 0.399 (w/%) Fe, 97.361 (w/%) Ni and 1.970

(w/%) Cu,Place (2): 0.355 (w/%) Fe, 1.640 (w/%) Ni and 98.005

(w/%) Cu,Place (3): 0.956 (w/%) Fe, 97.616 (w/%) Ni and 1.419

(w/%) Cu.Individual analysis places for the EDS analysis of

individual layers (Places (1), (2) and (3)) of the anti-corrosion coating have been selected centrally in eachlayer of the anticorrosion coating. In order to determinethe distribution of elements in the layers of the sampleV3-VP’s protective coating, EDS "mapping" was con-ducted (analysis of the distribution of chemical elementson the same surface sample area of the individualanti-corrosion coating layer). Figure 7 illustrates theSEM microstructure of the anticorrosion coating layer onmagnet sample V3-VP with the distribution of thedetected elements in those layers. We have determinedthat the upper layer of the anti-corrosion coating on the



Figure 5: Characteristic EDS spectrum of the sample V2-VV with the selected place of analysis (present anticorrosion coating magnetic cores)

Figure 4: Characteristic WDS spectrum of vibrator housing sample V2-V with the selected place of analysis

V3-VP magnet sample of the consists of three single-component layers (Ni, Cu, Ni), covering an Fe magneticcore. The distribution of Ni in two layers of the surfaceof the magnet is relatively even, though in certain areas(a few μm in size) the presence of Ni is significantlydiminished. The distribution of Cu in the layer betweenthe two layers of Ni is also fairly even; here we alsonoted certain areas (a few μm in size) with a significantlydiminished amount of Cu present. Further on, we carriedout the EDS analysis of representative samples of mag-netic cores on samples V1-VV, V1-ZV, V2-VV, V2-ZV,V3-VV, V3-ZV, V4-VV, V4-ZV, V5-VV, V5-ZV, V6-VV andV6-ZV to determine the presence and content of REEs inthe selected samples and the distribution of chemicalelements on the surface. An example of characteristicEDS spectrums of the sample vibrator V1-VV andspeaker V1-ZV’s magnetic cores with selected areas ofanalysis and contents of the detected elements is shownin Figure 8. The EDS microchemical analysis ofsamples V1-VV and V1-ZV revealed presence of REEs asfollows:Sample V1-VV: 2.005 (w/%) Pr, 8.094 (w/%) Nd and

7.130 (w/%) Gd,Sample V1-ZV: 2.437 (w/%) Pr, 9.953 (w/%) Nd and

1.179 (w/%) Gd.The comparison of the results exhibited the highest

number of different REEs in samples V1-VV and V1-ZV.In addition to Nd and Pr, which also separately occur inother samples, Gd has been identified in the aforemen-tioned samples (V1-VV and V1-ZV). In order to deter-mine how the REEs are distributed on the selectedsurface of the magnetic core, EDS "mapping"/analysis ofthe distribution of chemical elements was performed inthe same area of the sample magnet V1-VV. EDS "mapp-

ing" (Figure 9) shows a relatively even distribution ofthe elements Fe, Pr, Nd and Gd, and certain areas (a fewμm in size) partly certain areas with a significantlydiminished amount of the above elements (Fe, Pr, Ndand Gd) are visible. An overview of the REE content inother representative magnet samples without the protec-tive anti-corrosion layer is given in Table 3.17

Table 3: The levels in the samples ERZ magnets (w/%)

Representativesample of

magnet

The levels of detected rare earth elements(w/%)

Pr Nd GdV1-VV 2.005 8.094 7.130V1-ZV 2.437 9,.953 1.179V2-VV 0.670 11.587 -V2-ZV 2.156 9.460 -V3-VV 3.233 10.730 -V3-ZV 2.829 10.299 -V4-VV 3.233 10.730 -V4-ZV 2.323 12.016 -V5-VV 3.332 10.440 -V5-ZV 2.177 10.668 -V6-VV 2.865 9.863 -V6-ZV 1.100 11.791 -

By means of the EDS microchemical analysis of themagnetic core samples without the corrosion protectivelayers, except for sample V2-VV (significantly lowercontent of Pr), we found that, regardless of the mobilephone’s production year, there is no major discrepancy inthe content of REEs Pr and Nd (Table 3). Discrepancyoccurred only in samples V1-VV and V1-ZV, where Gdwas additionally identified (year 2015). We assume thatthis is due to the development of magnet manufacturingtechnology (new chemical composition and higherrequirements regarding the functional properties of themagnets). As for the vibrator samples V3-VV (year 2007)and V4-VV (year 2004), we detected the same REE



Figure 6: EDS characteristic spectrum of layers of anticorrosion coat-ing in sample V3-VP with selected places of analysis and contents ofthe detected elements (w/%)

Figure 7: SEM microstructure layers of anticorrosion coating samplein V3-VP with the distribution of the detected elements in those layers

content (in mass fractions, (w/%) (Pr, Nd)) despite diffe-rent production years of the mobile phones. We concludethat this is due to the same magnet manufacturer.17

4 CONCLUSIONS

Using Light and Electron Microscopy, we evaluatedthe microstructure of mobile phone components contain-ing REE. By using microchemical analysis methods, wedetermined the proportion of REEs. Our conclusions areas follows:

• Mobile phones are made of several components, ofwhich only the vibrator and the speaker contain suffi-cient amounts of REEs usable for recycling.

• The examined magnets of the vibrator and speakerare located in the housings. They consist of a anti-corrosion coating and the core.

• Microchemical WDS and EDS analyses of the vib-rator and speaker housing did not confirm thepresence of REE.

• Anti-corrosion coating of magnets is composed ofthree layers (Ni-Cu-Ni). Its thickness ranges from24 μm to 26 μm, the outer layer being Ni.

• The microstructure of magnetic cores we examined istypical for sintered materials. The estimated size ofthe rudimental crystal grains in the magnetic core isfrom 5.4 μm to 10.9 μm depending on the model andproduction year of the mobile phone.

• The magnetic core is composed of Fe-Nd-Pr andenriched with Gd in the newer mobile phones.

• WDS and EDS microchemical analysis, together withREE and Fe distribution on the selected surface, point

to the fact that the magnetic core is homogenous involume in its chemical composition.

• The conduct of the microchemical analysis wasdisrupted due to the impact of the magnetic REEs.This resulted in distortion and reduced resolution ofthe electronic image. Magnetic impact on the EDSmicrochemical analysis was negligible.

• The two main magnets (vibrator and speaker) in anindividual mobile phone have a REE content of13.5 % (w/%), representing a combined estimatedweight of 0.082 g.

• The chosen characterization methods (LM and SEMmicroscopy) in combination with microchemicalEDS and WDS analysis, are relevant for determiningthe presence and content of REEs in magnets ofdisused mobile phones.Provided that all parties (manufacturers, dealers,

users, processors, etc.) included in the life cycle ofmobile phones are made aware of the correct sorting andcollecting principles, specified by the European Direc-tive on WEEE (which among others include a 45 %collection quota of WEE, including mobile phones, an80 % processing quota and a 70 % recycling quota bet-ween the years 2015 and 2018) and taking into accountthe 210.3 million mobile phones released on the Euro-pean market in 2015 alone, it is theoretically possiblethat by using modern recycling technologies andprocedures we could extract up to 476,960 kg of copper,13,249 kg of silver 1,272 kg of gold and 477 kg of



Figure 8: Overview of characteristic EDS spectra of samples fromselected places of analyses, contents of the detected elements (w/%):a) the pattern V1-VV and b) the pattern V1-Zv

Figure 9: Overview of SEM microstructure of the magnetic coresample V1-VV with the distribution of the detected elements on thesurface

a)

b)

palladium. Considering the findings of the present study,that show the average REE content in the speaker andvibrator of a mobile phone is approximately 13.5 (w/%)and the total estimated REE weight is 0.082 g, we could,in theory, by using modern recycling procedures, extract4,345 kg, disregarding the amounts of REE found inother functional mobile phone components (circuit,microphone, display and camera).18

As for the economic and sustainability aspect of therecycling process and its justifiability, an additionaluptrend is expected from 2019 onwards. For this period,the European Directive on WEEE foresees a 65 % col-lection, 75 % processing and 55 % reusability andrecycling quota of the estimated more than 250 millionmobile phones being released on the market in 2018.13,18

Based on the reviewed scientific literature, otherstudies on the topic and the analyses and results of ourown research work, we can conclude that laboratoriesand special chemical procedures for REE extraction arerequired for the recycling of discarded mobile phones.As a consequence, incidental costs arise, which aredisproportionate to the quantity of recovered REEs andtheir economic value. Furthermore, REEs are not theonly valuable material usable for recycling and reuse.We must strive towards acquiring other secondary rawmaterial, including copper, silver gold and palladium, inaddition to REEs in the recycling process.9,20 Thus, wecan deduce that the recycling REEs from the componentsof discarded mobile phones is economically justifiable aslong as we also recover valuable secondary raw material(Cu, Ag, Au, Pd, Pt, etc.) in the process.

In addition to the economic aspect of recycling dis-carded mobile phones, we must take into considerationthe sustainability aspect of the matter, from whichrecycling discarded mobile phones is well-justified andcrucial. Moreover, we must take into account that thequantity of recovered REEs and other valuable rawmaterial is not the only positive effect. By recyclingdiscarded mobile phones, we also make a critical contri-bution to reducing the unregulated accumulation of WEEand to improving the resource efficiency, help regulatethe quantity of REEs on the market, assist the recoveryof valuable secondary raw material, and lastly consider-ably reduce negative effects on the environment, towhich we are bound by the European Directive onWEEE.18,20

Acknowledgements

We would first like to extend our thanks to theSlovenian Research Agency (ARRS), whose co-fundingenabled the research conducted within the framework ofthe Research Project (no. L2-5486) and Core ProgrammeP2-120 and Ministry of Education, Science and Sport,Republic of Slovenia (Programme MARTINA,OP20.00369). We would also like to thank the manage-ment and the technical assistance staff at the Departmentof Materials and Metallurgy of the Faculty of Natural

Sciences of the University of Ljubljana, as well as thoseat the University Centre for Electron Microscopy Mari-bor (UCEM), the Institute of Metals and Technology(IMT) and the Faculty of Mechanical Engineering inMaribor for enabling the research and providingexpertise. Last but not least, we would like to thank thethe Academic and Scientific Union of Pomurje (PAZU).

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